The invention relates to the production of fluids through well screens from multiple producing zones in a well, and more particularly, to the production of fluid from a well zone from which no production is desired until production from a lower zone has been completed or until the screen in the lower zone has been severely eroded by sand. An example of a system for accomplishing such selected production is the selecta-flow screen system sold by Baker Sand Control Company of Houston, Tex. The aforementioned system uses a regular screen in the lower zone which, upon initial completion of the well, is sealed with respect to one or more selectively operable screen segments in an upper zone by a packer and by a length of nonperforated inner pipe. The upper zone screens are normally isolated from communication with either the surface or with the lower screen by a solid or unperforated center pipe located on the screen axis. When the lowermost one of the upper screens is to be activated, a wire line plug is set in a nipple below the screen to be activated and the inner pipe opposite to the screen being activated is perforated. When each of the additional upper screens is to be activated, a plug is set in a nipple joining it to the screen below it to close off flow from below and a perforating tool is deployed and actuated to perforate the inner pipe opposite the screen being activated.